There are many electronic applications for which data needs to be transmitted at high speeds over band-limited channels. For example, data storage systems, servers, data communication systems, and digital video systems all need to provide high-speed serial links over band-limited channels. This can be accomplished by providing a transmitter at one end and a receiver at the other end of a “telecommunications channel” or “communication link.”
In telecommunications, inter-symbol interference (ISI) is a form of signal distortion wherein a transmitted symbol interferes with subsequent transmitted symbols. This is an unwanted phenomenon as the previous symbols have similar effect as noise, thus making the communication channel less reliable. That is, the presence of ISI may introduce errors at the receiver output. Therefore, in the design of telecommunication systems, an objective is to minimize the effects of ISI and thereby deliver the digital data to its destination with the lowest error rate possible, e.g., with the best signal-to-noise ratio (SNR).
Some ways to fight inter-symbol interference include, for example, adaptive equalization techniques. Adaptive equalization can be used to adapt to changing conditions of an incoming signal to provide more effective reduction of ISI. For example, one type of analog adaptive equalization technique uses Continuous Time Linear Equalizers (CTLEs), such as the MAX3800 series of products from Maxim Integrated Products of Sunnyvale, Calif. CTLEs can be used in communication links to compensate for the channel's frequency dependent loss which causes ISI.
While such equalizers operate adequately for their intended applications, they also exhibit certain drawbacks under some circumstances. For example, such equalizers may use complex blocks, creating increased cost and power consumption. These devices also typically use feedback to provide adaptive equalization, which can introduce stability issues and slow down the response of the equalization. Furthermore, these types of devices may have issues with long single-frequency signals, such as D10.2 signals in 8b/10b encoding. These types of devices also may attenuate the input signal after amplification, causing potential dynamic range issues.
These and other limitations of the prior art will become apparent to those of skill in the art upon a reading of the following descriptions and a study of the several figures of the drawing.